The present application is based on and claims priority from Japanese Patent Application Hei 11-350074 filed Dec. 9, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rotary electric machine such as a motor or a generator to be mounted in a ship or a vehicle.
2. Description of the Related Art
Recently, hybrid vehicles have been manufactured in order to protect the environment. A hybrid vehicle is driven by a motor while running at a low speed in a town or the like and is driven by an engine while running at a high speed in a suburb. There is a hybrid vehicle, such as a hybrid bus on a regular route, whose engine is switched off when the vehicle stops temporarily on a traffic signal. Such a hybrid bus is equipped with an idle-stop system for automatically stopping the engine. Incidentally, an inexpensive rotary electric machine that operates both as a motor and as a generator has been demanded to continuously drive a compressor and/or a power steering pump while the vehicle engine is stopped.
WO98/54823 or U.S. Pat. No. 5,998,903, which corresponds to WO98/54823, discloses a compact and powerful generator. Such a generator has a stator winding formed of a plurality of conductor segments, a stator core having two times as many slots as an ordinary generator. The conductor segments are connected so that one of the conductor segments that extended from one of a plurality of layers of a slot is connected to another that are extended from another layer of another slot. This arrangement improves the conductor""s space-factor and cooling effect of the stator winding, resulting in a stator winding of low resistance. In the above publication, there is an embodiment, in which windings that are disposed in the neighboring slots are connected in series to be connected to a rectifier bridge to provide a DC output power. There is another embodiment, in which windings disposed in the neighboring slots are connected in parallel to be connected to respective rectifier bridges to provide a composite DC output power.
In a vehicle rotary electric machine, there is a demand for increasing current capacity of each phase winding. For example, if the torque of a motor is increased, it is necessary to increase drive current supplied to the stator winding. It is also necessary to lower the resistance of phase windings of a generator to generate a large amount of current.
In view of the above subject, a main object of the invention is to provide a vehicle rotary electric machine that has a stator winding having a large current capacity.
Another object of the invention is to accommodate a small number of conductors in each slot and form a plurality winding sections connected in parallel, thereby increasing the current capacity of the stator winding.
Another object of the invention is to provide new conductor segments that are suitable for forming a parallel circuit of the winding sections.
Another object of the invention is to provide a vehicle rotary electric machine that can operate as both a motor and a generator.
According to a feature of the invention, a phase-winding is formed of a plurality of parallel winding sections, each of which is comprised of a plurality of conductors. This plurality of conductors is distributed to a plurality of neighboring slots.
As a result, the rotary electric machine can provide a sufficient torque characteristic, as a motor, and a sufficient output current characteristic, as a generator.
It is possible to provide five-phase or six-phase stator winding. However, parts of rectifying bridges or an inverter circuit should not be increased too many. From this point of view, three-phase stator winding is the most suitable. It is also possible to increase the number of the slots accommodating a plurality of the conductors forming a phase winding to more than two. However, it is necessary to take the size of the vehicle rotary electric machine into account, and two slots are the most suitable from this point of view. It is possible to increase the number of parallel winding sections to more than two. However, the working time for connecting such winding sections in parallel should be considered. From this point of view, two winding sections in parallel are the most suitable. Further, the number of conductors accommodated in each slot can be increased to more than two. However, current capacity, size, productivity of the rotary electric machine should be taken into account. For example, four conductors or less in each slot is the best suitable for a motor.
It is possible to provide a structure in which the winding sections are the same in phase with one another at opposite ends to be connected in parallel.
In general, if a winding formed of a plurality of series connected conductors disposed in a slot and another winding formed of a plurality of series connected conductors disposed in the next or neighboring slot are connected in parallel, current may flow from one to another because of phase difference between two winding. As a result, the efficiency of the rotary electric machine is not sufficiently high. However, the rotary electric machine according to the invention eliminates the phase difference, so that a sufficiently high efficiency can be maintained.
Further, a phase winding is formed of a first winding section and a second winding section. The first winding section includes a series circuit of a portion of a plurality of conductors disposed in one of the two neighboring slots and a portion of a plurality of conductors disposed in the other slot. The second winding section includes a series circuit of the remaining portion of the plurality of conductors disposed in the one slot and the remaining portion of the conductors disposed the other slot.
The first winding section may include a series circuit of a half of a plurality of conductors disposed in one of the two neighboring slots and a half of a plurality of conductors disposed in the other slot.
The conductors of the first winding section and the conductors; of the second winding section are connected in a manner corresponding to the phase angle, forming a diamond shape, which equalizes the phase angle of the first and second winding sections.
If the number of poles of said rotor is p, the number of phases of said multi-phase stator winding is n, the number of the neighboring slots for accommodating conductors of the phase winding of the stator winding is m, the total number of the slot is equal to or more than pxc3x97nxc3x97m.
The above structure is important to the vehicle rotary electric machine. For example, a 16-pole, three-phase and two-neighboring-slot type rotary electric machine has 96 slots. This type can provide a suitable size of a vehicle rotary electric machine. If a rotary electric machine has some empty slots, the number of slots becomes more than 96.
The above embodiment may include switch elements connected to the respective phase windings of the multi-phase stator winding. The number of the switch elements that are connected to respective phase windings is proportional to the number of the phases because each phase winding is formed of the winding sections connected to each other in parallel. For example, three-phase stator winding is connected to a three-phase bridge circuit. This structure can make the number and the size of the switching elements small. It is desirable to use diodes as the switching elements. A rectifier can be formed of diodes, and an inverter can be formed of transistors or MOS transistors.
The conductor may be a conductor segment connected at a coil end that is extended to an end of the stator core. The conductor segment is suitable to a stator having a small number of conductors in each slot. The conductors that are distributed to neighboring slots are connected in series to form a winding section, thereby providing a suitable number of coil-turns.
In addition, a plurality of coil ends is extended to an end of the stator core and is spaced apart from one another.
It is easy to line up the coil ends at a prescribed portion so that the coil ends can be spaced apart from each other. This arrangement is effective to lessen heat problems. It is also effective to provide an even arrangement of the coil ends. For example, it is possible to provide gaps for passing cooling air between the coil ends.
It is also possible to fill the gaps with resinous material. Preferably, the conductors disposed in the slots have a rectangular cross-section having longer radial sides.
The vehicle rotary electric machine can be provided with a booster for boosting output voltage generated by the stator winding in a low speed range. Further, a switching device can disposed. in the rotary electric machine to repeat grounding and opening of the output terminal of the stator winding.